Leather-like material and method of making the same



United States Patent Ofiice 3,294,579 Patented Dec. 27, 1966 3,294,579 LEATHER-LIKE MATERIAL AND METHOD OF MAKING THE SAME Shu-Tung Tu, Ipswich, Mass., assignor to United Shoe achinery Corporation, Boston, Mass, a corporation of New Jersey No Drawing. Filed May 9, 1963, Ser. No. 279,319 8 Claims. (Cl. 117140) This invention relates to a leather-like material having improved surface character and to a method of making the same.

In my earlier application Serial No. 170,225, filed January 31, 1962, now abandoned, entitled Leather- Like Material and Method for Making the Same, there is disclosed a process for making a strong leather-like material in which an aqueous suspension of swollen undissolved microscopic collagen fibers is caused to fill the interfiber spaces in a mat of intermeshed fibers, and thereafter by altering the conditions the fibers are deswelled and associated with each other as a larger collagen fiber structure. The collagen fiber structure thus formed extends through the mat of intermeshed fibers and is associated with them to reinforce them against displacement. The resulting sheet is strong and possesses many of the characteristics of leather. It has been found, however, that because of changes resulting in such sheets after deswelling the collagen fibers, surface finishes on such sheets may not retain the desired leather-like appearance when the sheet is stretched or flexed.

It is an object of the present invention to provide a reinforced leather-like sheet material having a surface character which retains its leather-like appearance when subjected to stretching or flexing and to provide a simple method for making this sheet material.

To these ends and in accordance with a feature of the present invention I have devised and improved leather-like sheet material and method of making it in which a high density of fibrous material is provided at and adjacent a surface of a reinforced fibrous mass to improve the as sociation of a finish with the fibrous mass to resist undesired changes of appearance on stretching or flexing.

In the present process fine short textile fibers are dispersed in a suspension of swollen collagen fibers of microscopic size and the mixed fiber suspension is applied to a sheet of intermeshed fibers. Both the collagen fibers and the textile fibers penetrate the sheet although a suspension of the textile fibers alone would not. Further to increase the fiber concentration of the sheet, there may be applied to either surface of the sheet a further quantity of a suspension of swollen collagen fibers. For the initial impregnation it is preferred to use a suspension in which the collagen fibers are highly swollen to carry and assist in the penetration of the sheet by the short fine textile fibers, and to use for the second impregnation a suspension of collagen fibers which are less swollen and are more readily held by the sheet. Optionally the sheet may he treated after the first impregnation to deswell the collagen fibers and leave the sheet in a more open condition so that it may be readily impregnated with a suspension of swollen collagen fibers. Thereafter the reimpregnated sheet is subjected to conditions effecting a desWellin-g and reaggregation of the collagen fibers.

In a sheet impregnated one or more times and subjected to deswelling, the reaggregated collagen fiber structure formed is associated both with the intermeshed fibers of the fiber sheet and with the hue short textile fibers from the suspension to hold them against displacement.

The short textile fibers used to increase the fiber concentration at the surface of the sheet may be any of a variety of known, preferably nonswelling or slowly swelling textile fibrous materials such as nylon, polyester (Dacron), wool, glass fiber, protein fibers such as zein, casein or special collagen fibers, e.g., chrome tanned collagen fibers and cellulosic fibers such as cotton or rayon. Fibrous material of low denier is desired, for example, from 1 to 3 denier and relatively short length, e.g., from about 0.1 to about 7 mm. preferably from 1 to 3 mm., may be used. Although an aqueous suspension of such fibrous material would merely form a substantially nonpenetrating layer if applied to an intermeshed fiber mat, it is found that in combination with an at least 0. 5 solids suspension of swollen microscopic collagen fibers in an aqueous medium, the short textile fibers will penetrate the fiber mat to an extent at least sufficient to hold them and ordinarily will penetrate from 1 inch to 4: inch depending on the retained openness of the mat. In many operations the short textile fibers may penetrate up to about one-half the thickness of a fiber mat to give a sheet material having densely packed fibers adjacent one surface. The ratio of added fibers to collagen fibers may be as high as 2 parts of the added fibers to 1 part of the swollen microscopic collagen fibers. While there is no lower limit on the ratio of added fibers to collagen fibers, from a practical point of view, in order to insure the desired increase in fiber concentration at the surface of the sheet, it is preferred to use not less than about 1 part of the added fibers to 10 parts of the collagen fibers in suspension. It is to be noted that the suspended swollen collagen fibers continue to penetrate through a mat even though the textile fibers are held after limited penetration so that the ratio of textile fiber .to collagen fiber will ordinarily be higher in the mat adjacent the treated surface than in the suspension.

Longer textile fibers, for example inch in length may be combined with a suspension of swollen microscopic collagen fibers; but these fibers may penetrate only to a limited extent leaving portions of the length of the fibers at the surface when a suspension containing them is applied to an intermeshed fiber mat. On deswelling of the collagen fibers a tough grain-like surface layer is formed, held to the surface both by the collagen fibers and by the penetrating portions of the textile fibers.

The microscopic collagen fiber suspension used in the present process may be any of the suspensions described in my copending application above referred to. As there described collagen material, for example, skin or hide is 'beaten in water under conditions which limit swelling of the collagen fibers to reduce the collagen to distinct noncolloidal microscopic fibers and form a suspension in which these fibers are capable of relatively free movement in the aqueous medium in which they are formed. Ordinarily the skin material is lightly tanned, for example, to an extent comparable to to preferably not over 3% of combined aldehyde such as formaldehyde, glutaraldehyde, or glyoxal based on the dried weight of the skin material. The fibers in the suspension thus formed may have a length of from about 0.01 nnn. to

not over about 4.0 mm. and preferably not over 1 mm. in length.

The suspension is adjusted to provide controlled swelling of the suspended collagen fibers. The term swelling in the special sense here intended refers to the phenomenon that the surfaces of the fibers become slippery and the fibers increase in thickness and decrease in length but remain as distinct fibers. The suspension is transluent. As in the above-referred to application the extent to which the collagen fibers in suspension are brought to a condition for effective penetration intoan inter-meshed fiber mat varies with the formaldehyde content and with the pH. With a given collagen fiber, penetration ability will increase from a minimum adjacent the isoelectric range along a curve which peaks about pH 2.0 on the acid side and at about pH 11.5 on the alkaline side of the isoelectric range and falls off on either side of the peaks.

A useful degree of swelling is obtainable at pH values about 0.5 of a pH unit outside the isoelectric range of the collagen fiber. Where the collagen fiber is obtained from hides which have been limed, the isoelectric range may be from about 4 to 5.5 while with hides which have not been limed the isoelectric range may be from about 7 to about 8. Ordinarily limed hides which are more readily available will be used and the following description sets forth conditions particularly useful with fibers from limed hides. Adjustment of pH values for use with fibers from other hides can be made readily by chemists. On the acid side of the range the pH of the suspension of collagen fiber from limed hide will ordinarily be kept in the range of from about pH 0.5 to about pH 3.5 and most desirably from about pH 2 to about pH 3.0. The higher portions of this range are used with the more highly swelling acids such as formic acid, acetic acid, citric acid, phosphoric acid and others.

Efiective swelling above the isoelectric range has been obtained in a suspension of collagen fiber fromlirned hide at a pH in the range of from about pH 6.0 to about pH 12 and more desirably from about pH 8 to about pH 10. The fiber suspension may be brought to this range by addition of alkaline reagents such as sodium hydroxide, tri-sodium phosphate, potassium hydroxide and-various other alkaline hydroxides and salts which do not form insoluble compounds with the collagen.

The extent of tanning of the hide material as with formaldehyde has been found to be an important factor in the bringing of the collagen microscopic fiber suspension into the desired state for effective penetration and ability to carry the fiber into a mat and retention of the dispersed fibers within the mat. Penetration ability decreases and retention of the fiber increases with increase in the extent of tanning. It has been found generally desirable to use collagen fiber tanned to an extent corresponding to about 0.2% to about 1.1% formaldehyde by weight based on the weight of the collagen fiber. Thus, it has been found that with a formaldehyde content of 0.2% by weight based on the weight of the hide material, fiber suspension at suitable pH values will penetrate well into a given fiber mat and will carry short textile fibrous material with the mat. Where the formaldehyde content is 1.1% by Weight based on the weight of the hide material, a proportion of the collagen fibers may be retained on the surface of the same fiber mat to which the suspension is applied and the suspension will be less effective in carrying short textile fibers into the mat. The preferred formaldehyde content range is from about 0.3 to about 0.6% by weight based on the weight of the hide material. Within this range the suspension penetrates most effectively and is effective to carry short textile fibers into the fiber mat.

To further improve the association of the short textile fibers, the collagen filbers and the fibers of the mat, there may be incorporated in the suspension very small particles of fibrous or film nature, for example, the particles known as fibrids. The nature and the mode of preparation of fibrids are described in US. Patent 2,988,782,

' issued June 20, 1961, in the name of Parrish et al. For

use in the present relation, fibrids of regenerated cellulose or of synthetic polymer material such as polyamides, polystyrene and other thermoplastic polymers having a melting point significantly lower than the melting point of the added fibers and the fibers of the mat are preferred. The particles or fibrids may be used in amount up to about the weight of the textile fibers in the suspension. After surface impregnation of the mat using a mixed suspension of short textile fibers, swollen collagen fibers and fibrids, the collagen fibers may be deswelled and the sheet dewatered. At a later stage the surface portions of the sheet may be subjected to heat to fuse at least partially .the particles or fibrids to cause them to establish bonds between the fiber materials of the sheet to hold them against displacement without markedly reducing the porosity of the sheet.

It is possible to include synthetic rubber or synthetic resin in the suspension to modify the properties of the final product. Also other emulsions, for example, fat liquor emulsions and liquid solutions or suspensions of various dyes or pigments may be included.

The retained openness of a mat during application of the suspension of collagen fiber and other fibers is an important factor in securing the desired penetration. A wide variety of intermeshed fiber materials both Woven and nonwoven may be used for association with the fiber suspensions. Ordinarily nonwoven fiber materials are preferred because of the greater variety obtainable in thicknesses, densities and openness to penetration by the suspension. The fibers of the mat are relatively long being of the order of one inch and langer and may be nylon, polyacrylic ester fibers (Orlon), polyester fibers (Dacron), polypropylene fibers, wool, extruded cellulosic fibers such as viscose or cellulose acetate and others. It has been found that best results are secured when the fibers are hydrophobic. In this connection a mat of longer collagen fibrous material which has been treated for example, by chrome tanning or other treatment to decrease its affinity for water may be used. Also natural cotton fiber preferably treated to decrease its affinity for water is usable.

Since an important aspect of the present invention is the manufacture of leather-like products, the intermeshed fiber materials are preferably in the form of relatively thin mats in which the fibers are in a relation providing relatively large interstitial spaces. The fiber mats preferably although not necessarily have been subjected to a treatment as with barbed needles to improve the intermeshing of the fibers. Fiber mats which have been subjected to needling have improved strength and resistance to delamination. However, there are needle holes and areas of low fiber content which have heretofore resulted in undesirable unevenness in sheet materials based on them. It appears that the presence of the short textile fibers in the collagen fiber slurry offers a material advantage in filling these holes and low fiber areas to .give a product of improved uniformity.

A fiber density and relation which have been found very satisfactory are those in nylon fiber mats having densities of the order of 4 ozs. per sq. yd. at a thickness of 0.15 inch and 6 ozs. per sq. yd. at a thickness of 0.175 inch. It is preferred that the fibers be relatively fine and fall in the range of from 1 to 5 denier with 3 denier being satisfactory. Other highly satisfactory materials are a 3 denier polypropylene fiber mat having a fiber density of 7 ozs. per sq. yd. and a thickness of 0.2 inch and a 3 denier polypropylene fiber mat having a fiber density of 2.5 ozs. per sq. yd. and a thickness of 0.125 inch.

Penetration of the suspension of textile fibers and swollen collagen microscopic fibers into an intermeshed fiber mass may be effected in a variety of ways. Thus the fiber mat may be disposed on a screen and the suspension forced in with the aid of pressure or suction. Suspensions having a collagen fiber solids content of for example, from about 0.5% to about 4% by weight solids may be used in this procedure. Still other procedures are available including spreading the suspension on the surface of the mat and working it in. The quantity of suspension to be applied to a given area of mat is selected to provide a retained collagen fiber content in the mat of at least about 5% by weight based on the combined weight of the fibers of the mat, the short textile fibers and the collagen fibers. The sum of the weights of collagen fibers and short textile fibers will range from about 15% to about 65% by weight based on the combined weights of the collagen fibers, short textile fibers and mat fibers.

Reduction of the acid or alkali content of the collagen microscopic fiber material within a fiber mass and removal from the fibers of the water of swelling may be effected by subjecting the fibrous mass to extraction with distilled water or a Water miscible volatile organic solvent such as acetone and other ketones, and lower alcohols such as methanol, ethanol and isopropanol to bring the pH to the isoelectric range. Treatment of the fiber mat with an aqueous solution of a buffer salt such as an acetate or phosphate butfer system is also effective to bring the pH to a value in the range of about 3.5 to about 6 at which reaggregation of the collagen microscopic fibers will occur with removal of the swelling water from the fibers. a solution having an ionic strength of about 0.2. Reaggregation may also be effected by treating the fiber mat with a 10% aqueous ammonium sulfate solution or by treatment with vegetable or mineral tanning agents to effect a deswelling of the fibers.

The deswelling of the collagen fibers in the mat gives a sheet which is firm and has a high degree of porosity. That side of the sheet to which the mixed fiber suspension was applied has as a high reinforcing fiber content which has been found to provide a firm anchorage for finishes.

Although for some purposes the sheet so obtained may be useful after tanning and finishing operations, a superior sheet is made in accordance with the preferred form of the present invention by further impregnating the sheet with an aqueous suspension of swollen microscopic collagen fibers. This further impregnation deposits additional collagen throughout the sheet to give greater fullness and plumpness. That is, the pores in the sheet after the first impregnation and, optionally, deswelling are capable of penetration by the swollen microscopic collagen fibers in a suspension and these collagen fibers may then be reaggregated by a deswelling treatment and will associate with collagen fiber already formed within the sheet. Sheets so formed have increased collagen fiber density throughout the sheet and a desirable firmness and plumpness after tanning and finishing operations. It is found also that the sheet with the increased collagen fiber density and with the textile fiber penetrating one side gives a superior action during lasting and better retention of its leather-like appearance during use.

The sheet material may be subjected to a needling operation at one or more stages in the course of manufacture. The needling operation involves penetrating at least the surface of the sheet with needle points having somewhat the character and size of steel phonograph needle points and a density of penetrations which may range from 600 to 6000 per square inch. The needling may be effected after the first impregnation, after a first deswelling, after the second penetration or after final deswelling. The needling after the first swelling has the double action of improving the association of the fibrous materials and of providing somewhat greater penetration ability by the subsequently applied collagen fiber suspension. The needling will ordinarily be effected from the side on which the first, that is, mixed textile fiber and collagen fiber, sus- It is desirable in the use of buffer systems to use .been pulled into the mat.

pension was applied and imparts to that surface the appearance of pores as well as providing for a desirable cooperative action between applied finishes and the fibers displaced from the holes by the action of the needles.

The fiber mat is compacted and reduced in thickness in the course of penetration by the suspension and reaggregation of the collagen material so that, for example, starting with a 4 oz. per sq. yd. nylon fiber mat with an initial thickness of 0.15 inch, after penetration by suspension aud reaggregation of the collagen material, the thickness will have reduced to from about .015 to about .03 inch. correspondingly a sheet prepared from a 6 oz. per sq. yd. nylon mat having an initial thickness of 0.175 will form a sheet about 0.04 inch in thickness. This reduction in thickness is due in considerable measure to the action of the suspension in being forced into the mat. A further action which influences the reduction in thickness is the pulling together of the collagen material by water bonding; and this factor may range from very slight where water is extracted from the sheet by solvent to relatively large where a substantial portion of the water is removed by evaporation.

The sheet material is preferably subjected to tanning with mineral tanning agents such as chrome tanning liquors or with vegetable tanning agents. Because of the collagen deswelling action of tanning agents it is possible to effect both reaggregation and tanning at the same time. Conventional leather tanning procedures may be used and the tanning may be carried out either in an aqueous tanning medium or a solvent type tanning medium.

The following examples are given to aid in understanding of the invention and it is to be understood that the invention is not restricted to the particular materials, proportions or procedures set forth therein.

Example I A 5% solids aqueous suspension of collagen fibers of microscopic size was prepared by the procedure shown in the above-referred to application of Tu involving light formaldehyde tanning of limed hide and reduction of the hide material to a suspension of microscopic size fibers by beating in Water. The fibers had a formaldehyde content of 0.4% by weight based on the weight of the collagen fibers and the suspension was adjusted to a pH of about 2.0. 3 grams of short nylon fibers, mixed 1 and 2 denier and random lengths up to about 1 mm., were dispersed in 720 grams of water. The nylon fiber suspension and grams of the collagen fiber suspension were combined and the mixture was vigorously agitated to mix the fibers uniformly.

A sheet 7 inches in diameter of a nonwoven intermeshed fiber mat of 3 denier nylon fibers having a weight of 7 /2 oz. per sq. yd.-and -a thickness of 0.175 inch was nylon fibers was deposited on the fiber mat and leveled. Suction to a value of 27 inches of mercury was applied to the mat and in two minutes the applied suspension had A portion of the collagen fibers was in the liquid drawn from the mat but none of the nylon fibers came through.

After the suspension had been pulled through the mat, portions of 400 cc. of dry acetone were drawn through the mat to remove water and to effect the reaggregation of the microscopic collagen fibers of the suspension. After evaporation of the acetone, the dried weight of the mat was 15.0 grams, comprising 7.8 grams of initial mat gkeight, 3 grams of nylon fiber and 4.2 grams of collagen Thereafter the mat was removed from the filter bed and on examination it was found that the collagen fiber was distributed through the thickness of the mat and that the nylon fibers had penetrated about one-third of the thickness of the mat.

The mat was placed on the filter bed in reversed position that is, with the side to which the mixed fiber suspension had been applied disposed against the bed of the filter.

450 grams of a similar collagen fiber slurry containing 2% collagen fibers at pH 2 was deposited on the mats surface and pulled into the mat by the application of suction. Five minutes were required to pull the suspenslon into the mat. The mat was treated with dry acetone as before. The dried weight was 18.0 grams.

The resulting sheet materialafter removal from the filter bed resembled a solvent dried skin material and had a collagen content of 7.2 grams and a nylon fiber.

content of 3 grams on 42% collagen and 16.7% short nylon fiber based on the total weight of the mat. The mat was well filled with collagen fiber and the face of the mat to which the mixed suspension had been applied was found to be quite firm.

The sheet material was subjected to tanning by immersion in a standard buttered chromium tanning liquor containing 0.25% by weight chromium calculated as Cr O and /2% by weight of sodium formate and having a pH of 4. The sheet was removed from the tanning liquor and allowed to stand overnight in a covered receptacle. The sheet was then washed in water for three successive periods of 15 minutes.

After washing the sheet was dried by immersion in successive acetone baths and the dried sheet was then immersed in a 4% by weight solution of oleic acid and acetone for 1 /2 hours. Thereafter the sheet was removed and allowed to dry at room temperature. The dried sheet was similar to a chrome tanned skin and its physical properties were in the range of leather.

The sheet was subjected to a light buffing operation with fine sandpaper on the surface to which the mixed suspension was applied and thereafter Was given a conventional leather finish. The finished sheet was suitable for shoe manufacture.

Example II The procedure of Example I was followed; but 2 grams of nylon fibrids were added to the nylon fiber suspension before mixing with the collagen fiber suspension.

The slurry of collagen fiber, nylon fibers and nylon fibrids penetrated the fiber mat in approximately the same manner as did the mixture of collagen fibers and nylon fibers alone and the extent of penetration of the nylon fibers and the nylon fibrids was about one-third of the thickness of the sheet.

After following the procedure to the point of tanning the twice impregnated sheet and removing water from this tanned sheet, the sheet was subjected to a plating operation on the side to which the mixed collagen fiber slurry, nylon fibers and nylon fibrids had been applied. This plating operation involveda temperature of 385 F. and a pressure of 1000 lbs. per sq. inch for about one minute.

The finished sheet resembled a good grade of leather and it was found that the surface was tighter and the character of the sheet when bent or stretched was somewhat improved even over the sheet prepared according to Example I.

Example Ill Two grams of high tenacity random-out rayon flock in which the maximum fiber length was Mr inch and one gram of random-cut cotton flock of which the maximum length was /s inch were suspended in 200 ml. of water. This suspension was combined with 200 grams of a microscopic size collagen fiber slurry prepared by dilution of 80 ml. of the 5% solids suspension used in Example I, with 120 ml. of water. A sheet 7 inches in diameter of nonwoven intermeshed fiber mat of three denier polypropylene fiber, having a weight of 2 /2 oz. per sq. yd., and a thickness of 0.125 inch, was disposed on a filter bed provided with means for applying suction. initial weight of the mat was two grams.

The above-prepared mixture of collagen fiber and other fiber was spread on the mat and leveled. Suction to a value of 27 inches of mercury was applied to the mat. In less than two minutes the mat was wet through by the suspension.

Thereafter three successive 400 cc. portions of dry acetone were drawn through the mat to remove water and to effect the reaggregation of the microscopic size collagen fibers of the suspension. After evaporation of the acetone the dried weight of the mat was 5.9 grams comprising two grams of initial mat weight, two grams of rayon fiber, one gram of cotton fibers and 0.9 gram of collagen fiber.

Thereafter the mat was subjected to tanning by immersion in a standard buffered chromium tanning liquid containing 0.25% by weight chromium calculated as Cr O and /2 by weight of sodium formate and having a pH of 4. The sheet was removed from the tanning liquid and allowed to stand overnight in a covered receptacle. The sheet was then washed in water for three successive periods of fifteen minutes.

Thereafter the sheet was finished by the procedure followed for finishing the sheet in Example I. A strong flexible leather-like sheet material having a high fiber density and a grain-like appearance on the surface to which the mixed suspension was applied was obtained.

Example IV 900 grams of the mixed collagen fiber and nylon fiber suspension prepared in accordance with Example I was applied to a sheet 7" in diameter of a nonwoven intermeshed fiber mat of 3 denier nylon fibers having a weight of 7 /2 oz. per sq. yd. and a thickness of 0.175" and was pulled into the mat by applying suction on a filter bed as in Example I. The initial weight of the mat was 7.8 grams.

After the suspension had been pulled into the mat, 450 grams of a similar collagen fiber slurry containing 2% collagenfibers but no nylon fibers and with its pH adjusted to 3.70 was deposited on the mats surface, the mat The being in its original position on the filter bed and pulledinto the mat by the application of suction.

After the suspension had been pulled into the mat, three successive portions of 400 cc. of dry acetone were drawn through the mat to remove water and to effect reaggregation of the microscopic collagen fibers of the suspension. After evaporation of the acetone, the dried weight of the mat was 18.6 grams comprising 7.8 grams of initial mat weight, 3 grams of nylon fiber and 7.8 grams of collagen fiber.

Thereafter the mat was removed from the filter bed and on examination it was found that the collagen fiber was distributed through the thickness of the mat and that the nylon fibers had penetrated about one-third of the thickness of the mat. The face of the mat to which the gnixed suspension had been applied was found to be quite Thereafter the sheet was tanned and finished following the procedure used in Example I. A strong flexible leather-like material was obtained.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. The process of forming a leather-like material including the steps of applying to a side of a sheet of intermeshed textile fibers a quantity of an aqueous suspension of short textile fibers and at least /2 part by Weight of swollen distinct fine collagen fibers of microscopic size to one part by weight of said short textile fibers to introduce collagen fibers and short textile fibers into spaces between said intermeshed textile fibers in a portion of the thickness of said sheet extending in from said side, said suspension having a pH outside the isoelectric range of said collagen fibers; and removing swelling water from said collagen fibers to reaggregate them into a larger collagen fiber structure binding said intermeshed fibers and short textile fibers.

2. The process of forming leather like material includmg the steps of applying to the first side of a sheet of intermeshed textile fibers a first quantity of an aqueous suspension comprising short textile fibers and at least /2 part by weight of swollen distinct fine collagen fibers of microscopic size to one part by weight of said short textile fibers to introduce collagen fibers and short textile fibers into spaces between said intermeshed textile fibers in a portion of the thickness of said sheet extending in from said first side, removing swelling water from said I collagen fibers to reaggregate them into a larger collagen fiber structure resisting displacement of said short textile fibers and said intermeshed fibers and to leave open spaces in those portions of said sheet penetrated by said first quantity of suspension thereafter applying to the second side of said sheet a second quantity of an aqueous suspension of swollen distinct fine collagen fibers of microscopic size at least partially to fill open spaces in said sheet and removing swelling water from said second quantity of collagen fiber suspension to reaggregate the fibers into a larger collagen fiber structure, said suspensions having collagen contents of at least 0.5% by Weight and having pH values outside the isoelectric ranges of said collagen fibers.

3. The process of forming leather-like material including the steps of applying to a side of a sheet of intermeshed textile fibers a first quantity of an aqueous suspension comprising short textile fibers and highly swollen distinct fine collagen fibers of microscopic size to introduce collagen fibers and short textile fibers into spaces between said intermeshed textile fibers in a portion of the thickness of said sheet extending in from said side, said suspension being at a pH adjacent the peak penetration value for said collagen fibers and containing at least /2 part by weight of collagen fibers to one part by weight of said short textile fibers, thereafter applying to the same side of said sheet a second quantity of an aqueous suspension of swollen distinct fine collagen fibers of microscopic size at least partially to fill open spaces in said sheet, removing swelling water from said collagen fibers to reaggregate the fibers into a larger collagen structure, said suspensions having collagen contents of at least 0.5% by weight and having pH values outside the isoelectric ranges of said collagen fibers. j

4. A process of forming a leather-like material including the steps of applying to a first side of a sheet of intermeshed textile fibers aquantity of an aqueous suspension comprising short textile fibers and at least /2 part by weight of swollen distinct fine collagen fibers of microscopic size to one part by weight of short textile fibers to introduce collagen fibers and short textile fibers into spaces between said intermeshed textile fibers, said short textile fibers penetrating a portion of the thickness of said sheet extending in from said first side at least 6 inch, contacting said sheet with water-miscible volatile organic solvent toremove swelling water from said collagen fibers to reaggregate them into a larger collagen fiber structure resisting displacement of said short textile fibers and said intermeshed fib'ers and to leave open spaces in portions of said sheet penetrated by said first quantity of suspension, thereafter applying to the other surface of said sheet a second quantity 'of an aqueous suspension of swollen distinct fine collagen fibers of microscopic size and causing said suspension to penetrate and at least partially to fill open spaces through the thickness of the said sheet contacting said sheet with a Water-miscible volatile organic solvent to remove swelling water from said second quantity of collagen fiber suspension to reaggregate the fibers into a larger collagen fiber structure, said suspensions having collagen contents of at least 0.5% by weight and having pH values outside the isoelectric ranges of said collagen fibers.

5. A process of forming a learner-like sheet material including a sheet of intermeshed textile fibers having a high concentration of fibers filling spaces between said intermeshed fibers at and adjacent a surface of said sheet which comprises the steps of introducing into said surface of said sheet an aqueous suspension of a mixture of swollen distinct fine collagen fibers of microscopic size and short fine textile fibers, said suspension of collagen and textile fibers having a pH at least 0.5 of a pH unit outside the isoelectric range of said collagen fibers and comprising at least about 0.5% by weight of collagen fibers based on the weight of said suspension, said collagen fibers being present to the extent of at least about /2 part by weight to one part by Weight of said textile fibers and thereafter removing swelling water from the collagen fibers of said mixture in said mat to reaggregate them into a larger collagen fiber structure associated with said intermeshed fibers and said textile fibers to reinforce them against displacement.

6. A process of forming a leather-like sheet material including a sheet of intermeshed textile fibers having a high concentration of fibers filling spaces between said intermeshed fibers at and adjacent a surface of said sheet which comprises the steps of introducing into said surface of said mat an aqueous suspension of a mixture of swollen distinct fine collagen fibers of microscopic size and textile fibers having a thickness of from 1 to 3 denier and a length of from about 0.1 mm. to about 4 mm., said suspension having a pH at least 0.5 of a pH unit outside the isoelectric range of said collagen fibers and comprising from about 0.5% to about 6% by weight of collagen fibers based on the weight of said suspension, said collagen fibers being present to the extent of from about /2 to about 10 parts by weight to one part by weight of said textile fibers, and thereafter removing swelling water from the collagen fibers of said mixture in said mat to reaggregate them into a larger collagen fiber structure associated with said intermeshed fibers and said textile fibers to reinforce them against displacement.

7. An open-fibered leather-like sheet material having densely packed fibers adjacent a surface providing a firm tight surface, said sheet material comprising a base sheet of intermeshed relatively long textile fibers, short fine denier textile fibers in spaces between said intermeshed textile fibers in portions of said sheet extending in from one side and a collagen fiber structure associated with said intermeshed textile fibers and said short textile fibers extending through said sheet, said collagen fiber structure constituting at least about 5% by weight and the sum of the weights of collagen fiber and short textile fibers constituting from about 15% to about 65% by weight, said weights being based on the combined weight of the textile fibers and the collagen fiber structure, the weight of said short textile fibers being not less than 10% of the weight of said collagen fiber structure and said collagen fiber structure possessing the special association with said textile fibers secured by formation in situ from an aqueous suspension of a mixture of said short textile fibers and fine distinct swollen collagen fibers of microscopic size by removing the swelling water from the collagen fibers to reaggregate them into a larger collagen fiber structure resisting major displacement of the textile fibers of said sheet.

8. An open-fibered leather-like sheet material having densely packed fibers adjacent a surface providing a firm tight surface, said sheet material comprising a nonwoven base sheet of intermeshed relatively long textile fibers, short textile fibers of from one to three denier and 0.1 to 4 mm. in length in spaces between said intermeshed textile fibers in portions 'of said sheet extending in from one side at least & of an inch but less than one-half the thickness of said base sheet, and a collagen fiber structure associated with said intermeshed textile fibers and said short textile fibers, said collagen fiber structure constituting at least about 5% by weight and the sum of the weights of collagen fiber and short textile fibers constituting from about 15% to about 65% by weight, said weights being based on the combined Weight of the textile fibers and the collagen fiber structure, the Weight of said shorit textile fibers being from A to four times the weight of said collagen fiber structure, and said collagen fiber structure possessing the special association with said textile fibers secured by formation in situ from an aqueous suspension of a mixture of said short textile fibers and fine distinct swollen collagen fibers of microscopic size by removing the swelling water from the collagen fibers to reaggregate them into a larger collagen fiber structure resisting major displacement of the textile fibers of said sheet.

References Cited by the Examiner UNITED STATES PATENTS 2,490,001 11/1949 Jayne et al. 260-77 3,169,885 2/1965 Golodner et a1. 117l35.5 3,223,551 12/1965 Tu 1l7l40 WILLIAM D. MARTIN, Primary Examiner.

T. G. DAVIS, Assistant Examiner. 

1. THE PROCESS OF FORMING A LEATHER-LIKE MATERIAL INCLUDING THE STEPS OF APPLYING TO A SIDE OF A SHEET OF INTERMESHED TEXTILE FIBERS A QUANTITY OF AN AQUEOUS SUSPENSION OF SHORT TEXTILE FIBERS AND AT LEAST 1/2 PART BY WEIGHT OF SWOLLEN DISTINCT FINE COLLAGEN FIBERS OF MICROSCOPIC SIZE TO ONE PART BY WEIGHT IF SAID SHORT TEXTILE FIBERS TO INTRODUCE COLLAGEN FIBERS AND SHORT TEXTILE FIBERS INTO SPACES BETWEEN SAID INTERMESHED TEXTILE FIBERS UB A PORTION OF THE THICKNESS OF SAID SHEET EXTENDING IN FROM SAID SIDE, SAID SUSPENSION HAVING A PH OUTSIDE THE ISOELECTRIC RANGE OF SAID COLLAGEN FIBERS; AND REMOVING SWELLING WATER FROM SAID COLLAGEN FIBER TO REAGGREGATE THEM INTO A LARGER COLLAGEN FIBER STRUCTURE BINDING SAID INTERMESHED FIBERS AND SHORT TEXTILE FIBERS. 